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dirty valve and ring job -- with pics
Topic Started: Jan 21 2015, 10:45 PM (5,347 Views)
perfesser
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Elite Member - Former Metro owner

brush
Jan 25 2015, 12:56 AM
atm though, getting a bore gauge would almost double the cost so far. it does make sense that in order to spec things out -- whether the micrometer i have is accurate enough or not -- would require some sort of t-gauge tool like the pics from perfessor's post. someone was suggesting some kind of compass with a sideways point on the tips -- but, also, that would be a hack.

frankly, for my 100% first time tear-down, i think my goal will be what hanuman said way back when: just hone the cylinders, re-ring, and replace the valves. and, um, maybe i'll try that "hard acceleration" wear-in trick from the link in your thread, perfessor, in case it helps the rings seat better.
Harbor Freight has a usable set of 6 measuring tools for under $10-. Look up item #94447. They include internal and external calipers, depth gauge, vernier caliper and more. There's no excuse for not knowing what your engine's specs are! If you have a problem, which is possible, you'll kick yourself a block and a half if you passed on this!! (Not to mention that any problems you may encounter will cost a lot more than ten bucks.)

Also check out item #5649 - Telescoping gauge set from 5/16" to 6" ($14.99), and item #66512 - a set of 3 micrometers covering 0" to 3" (on sale for $39.95). Both of these last two you may have seen in my rebuild thread. I could have spent 20 times this much for premium tools, but these do everything I need them for. So for the price of a good used alternator you could have all the measuring tools you'll ever need.
Edited by perfesser, Jan 25 2015, 02:29 PM.
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billay
New Member
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I did mine(1994 metro 3cyl) in february 2012 1 used valve, hand lapped in, new rings an rod bearings, honed cyl about a minute each. 38k trouble free miles later still going every day.Super Tech oil changed every 3k has not used any yet.Been on three trips over 1k miles very happy with it.55mpg on hwy 45 to 50 around town.(XFI cam.)
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brush
Member
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hi folks,

well, unexpected busy, but here's more updates. first some pics, then some questions.

cleaned up the pistons:

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and finished cleaning the valve seating area:

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then hand-lapped the valves:

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and ringed the pistons:

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i also ended up taking perfessor's advice and buying the t-gauge set ($15), along with the digital caliper nominally good to .0005". i will say that the process of finding exactly the middle of the bore, at the right height and perfectly level, seems to me to be the greatest source of error -- significantly more than the accuracy of the tool. at any rate, these are my only-slightly trustworthy measurements:

#1: 50mm: x: 2.9150" y: 2.9150
95mm: x: 2.9135 y: 2.9130

#2: 50mm: x: 2.9130 y: 2.9115
95mm: x: 2.9135 y: 2.9105

#3: 50mm: x: 2.9140 y: 2.9155
95mm: x: 2.9140 y: 2.9145

again, i don't 100% trust these -- but they are within the tolerance of 0.0039" for out-of-round or taper -- and even w/in the recommended tolerance of .0025". they're also less than the 2.919" listed, i believe, as the max diameter.

pistons also seem good -- #1: 2.9120; #2: 2.9130; #3: 2.9120.

the standard rings (evergreen, thanks hanuman!) i have are right at the low end of end gap.

how do i correctly calculate piston to wall clearance? the tolerances for the cylinder and piston do not seem to match the 0.0015" max clearance, unless i'm misunderstanding something about how to do it?

that's question #1!

question #2: as noted before, cylinder #3 has stains/glazing that i assume are from blow by. i've honed incrementally about 4 times for a total of perhaps 3 minutes, and a significant proportion of the stain/glaze is gone. i'm concerned about honing too much, and making the piston/wall gap even bigger. thoughts? here's a picture of the stain currently (you might be able to see the original stain in the earlier batch of photos from teardown.)

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so -- should i keep going? is 5 or 6 minutes of honing a concern for changing the diameter of the bore? (i'm using the spindle-stones type of hone, a loaner from autozone.) so far, there's no obvious change when i measure. i think i'll keep going, but thought i'd toss it out there.

fwiw, crosshatch is still visible in the other two cylinders from previous rebuild. final note: the engine is stamped "222", but the pistons are stamped "B2 - B1 - B2" -- and it's the #2 cylinder, with the "wrong" piston, that had no evidence of oil leakage. thoughts?

thanks!
.b
Edited by brush, Jan 28 2015, 10:33 PM.
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Woodie
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Too much honing already. Get oversized pistons and have it bored out to match them.
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brush
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reminder: i've not done 5-6 mins, i've done 2-3.

btw HUGE thanks to freegeo, who sent me an oil check valve. AWESOME!
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brush
Member
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ok, here's an offering.

i just went and re-measured cylinder #3 carefully after the hone. i get

50mm: x: 2.9130 y: 2.9165
95mm: x: 2.9140 y: 2.9140

this means a couple things:
1) clearly, my measuring is accurate to at most .001", since the bore could not have gotten SMALLER.
2) still, 2-3 minutes of honing did not make things measurably wider.

since according to this measure i'm already right near the limit of the out-of-round on the upper measurement, so i'll stop honing at this point.

but i have a theory i'd like to offer. it's radical, and i fully admit it's influenced by me being a cheapskate. at the same time, i'd like you to consider it.

theory: 0.0008 - 0.0015" is the piston-to-cylinder clearance tolerance for *factory* (or machined) parts. note how in the FSM pics i've seen this tolerance is listed right next to the high and low values for the factory piston diameter and factory cylinder diameter. in particular, this is a *minimum* value to avoid sticking at high temp.

the tolerance value for wear, in this theory, is determined by the tolerance for max cylinder bore -- 2.9193" i think. combine with the out-of-round/taper tolerance (0.0039"), and the ring end gap, this gives a sense of how much wear is ok before re-boring.

this is just a theory. i'm willing to test it, by putting back my engine and reporting how things go. admittedly, i'll be leaving that discolored deformity in the #3, which at this moment worries me more than piston clearance, but...

i'd love to hear thoughts about this. i realize it's slightly scandalous, but honestly i can't otherwise understand the discrepancy between the clearance number and the other wear tolerances.
Edited by brush, Jan 29 2015, 02:33 PM.
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myredvert
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myredvert

Quote:
 
but i have a theory i'd like to offer. it's radical, and i fully admit it's influenced by me being a cheapskate... ...i'd love to hear thoughts about this.
It's also likely being influenced by your current feelings of inconvenience and disappointment - all things that typically don't lead to making the best decisions. I believe one of the sub-stages of denial described in the Kubler-Ross engine rebuild book "the Seven Stages of Engine Death" is when you try to make up theories dependent on the idea that the design engineers have made some type of "oversight" by not presenting us with the proper and different specs that apply to rebuilds, in order to rationalize why cutting before measuring (ordering parts before measuring) wasn't a common mistake that you made. :dunno

It sounds to me like you already know the answer to your own question, but you really want someone else to tell you that the engineering that went into the engine isn't that important or that the engineers overlooked something by not providing us with applicable specs for a rebuild and you have discovered this mistake, and that everything will "turn out just as well" if you forge ahead. It might be ok, but it probably won't be the same.

The real question you should be asking yourself at this point is, what do you really want and expect the ultimate condition of your engine to be a product of? Engineering specifications defined by the engine designers, or home made theories devised only after finding yourself in a possibly inconvenient situation?

If you want and can afford to have the work done properly and enjoy the performance of a properly rebuilt engine, have it measured by a professional, get the appropriately sized pistons if necessary, and have them bore it to the exact size to get good tight tolerances, as Woodie already said. You are THIS close to being able to get your tolerances on the tight end of spec, so if that's what you really want, here's your chance. If you will be satisfied with something less or simply can not afford to finish the work and build an engine on the "better" end of the spec range, go ahead and put it back together the way it is, and, if necessary adjust your performance expectations accordingly and start making plans for how you will rebuild one better next time. You may very well get a serviceable engine that will perform acceptably and still last longer than your car may.

But stop wasting your time by trying to "re-explain" the professional engineering that went into the design and specs - that can only lead to bad decisions and greater disappointment later when you learn your choice to depend on home made engineering theories weren't quite up to Suzuki engineering standards.
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perfesser
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Elite Member - Former Metro owner

:+1 :thumb
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chessir


I fudged around my first time rebuilt just like brush is doing and was wildly successfull bringing 2 dead and nonstarting metros to life again getting me from a to b for over a year now. This is the fun way to introduce metro rebuilding. Some guys on here seem to want you to do an immediate professional rebuilt at elevated cost. Whereas the beginner just wants to do a quick and dirty to revive a dead metro to go from a to b. The beauty of the metro rebuilt is that this quick and dirty is possible and an enjoyable introduction. It's an excellent way to hook a metro owner into a lifetime member to perfecting the engine rebuilt process with the expertise of our dedicated gurus.

Sorry, I did not mean to repeat what Redvert stated. Apearantly we both responded simultaneously.

Edited by chessir, Jan 29 2015, 09:35 PM.
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brush
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thanks redvert, perfesser, and chessir. i agree: reboring and getting oversize pistons would be a preferable alternative, AND it's difficult for the budget i'm on. as i said to someone on PM, i'm ok pulling this engine apart in a few months if i have to -- for now, i think i need to get it running. i don't have grand expectations.

i've reassembled the valvetrain and put the #1 piston back in. pics to follow soon. i have a bunch of o-rings and gaskets from the rebuild kit, such as the cam and crank seals, but i've had no leaks in the past and may pass on doing these when they involve disassembling additional things -- unless anyone has suggestions of gaskets/seals that are especially useful at this stage. (of course, i'll regasket the exhaust, intake, head, and valve cover. i have an oil pan gasket, but believe RTV-only is better?)

all that said: i remain genuinely curious about the compatibility of the piston/wall clearance and (for example) the taper.

if the taper is, say, .0025", ie. well within tolerance, and the piston is just BARELY able to squeeze in at the bottom, then the clearance is going to be AT LEAST .0025" at the top. ie. well over the 0.0008" - 0.0015" spec. how does this make sense?

similarly, if the piston is at maximum allowed size (around 2.9142 i believe), and the cylinder is at 2.9170, well within the wear maximum of 2.9193, then the clearance is 0.0028 -- again, way over 0.0015".

so what is the point of these taper or max diameter sizes?

i'm genuinely curious. thanks, folks!
Edited by brush, Jan 29 2015, 10:17 PM.
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snowfish
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Basic GearHead

At this point, what taper spec is mute issue. Your plans are to re-assemble as is. The cam and crank seal require no additional dis-assembly. Use them. Keep you work environment as clean as possible. And then cleaner. Remove All old gasket material. Keep all parts as clean as possible. Parts need to be surgically clean. Take your time and double check your work. UltraGrey makes a great gasket dressing. Just keep it thin. Install head gasket dry. Use your torque wrench. It will run. Probably better than it did. Keep us posted. :popcorn
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perfesser
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Elite Member - Former Metro owner

Do not scrimp and cheap out on the torque wrench!! You can cut a lot of corners, but don't cut it there! Get yourself a good one.
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chessir


Do not mistake the metric torque wrench for the English like I did Omg!!! Senior citizen with declining eyesight. Lol
Edited by chessir, Jan 30 2015, 12:52 AM.
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Woodie
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brush
Jan 29 2015, 01:10 PM
reminder: i've not done 5-6 mins, i've done 2-3.
1 minute of honing is too much.
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RONNIEREDLINE
METRO MAD MAN

i agree with woodie.
you should not hone for to long, just enough to make a cross hatch in the cylinder, a stain doesnt harm anything, but id find out why? thats a big why to find out but i would.
honing never fixes anything but a cheap , down and dirty rebuild.
honing will only make the problem worse if you do it to long.
just my 2 cents worth
redline
Edited by RONNIEREDLINE, Jan 30 2015, 06:40 AM.
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